Drying apparatus



1941- A. c. BEARDSLEE ETAL DRYING APPARATUS F fliled May 19, 1958INVENTOR ARTHUR C. BEARDSLEE 2 BY GZR/GE W LSON A TTZRNEY Patented Oct.21, 1941 DRYING APPARATUS Arthur C. Beardslee, Arcade, and George W.Wilson, Watertown, N. Y., assignors to The Borden Company, New York, N.Y., a corporation of New Jersey Application May 19, 1938, Serial No.208,948

Claims. (Cl. 159-11) The invention relates to the drying of heavysuspensions of solid material in liquid vehicles. More particularly, itrelates to improvements in apparatus for drying cereal products, feed,and similar products which are insoluble or only partly soluble.

In drying products of the class described, it is the general practice toemploy heated drying rolls or drums arranged horizontally, the materialbeing fed downwardly between the rolls and later stripped therefrom inany convenient manner. The rolls are arranged with their axes inparallelism, and their adjacent surfaces are separated by an amountwhich varies in accordance with the type of material being dried.Usually dams are provided at the opposite ends of therolls so that thematerial may accumulate in the reservoir thus formed, providing acontinuous supply. In order to dry successfully certain products, suchas cereal mixtures, products containing whey and casein or similarproducts, it has been found necessary to space the rolls so far apartthat a considerable quantity of the admixture drops through the openingbetween them or drips from the rolls. This results in considerable wastewhich, in the case of certain of these products,- assumes suchproportions that the drying operation becomes impracticable.

It is an object of our invention to provide apparatus for dryingproducts of the character described which overcomes thisdisadvantage'and which embodies other improvements over apparatus knownheretofore.

A further object of the invention is to provide means for drying heavysuspensions rapidly and at low cost.

A more particular object is to provide means for drying suspensions ofsolids in liquids in the use of which excess material dripping from thedrying surfaces is not wasted.

A further object is to provide improvements in "The adjacent surfaces ofthe rolls move downwardly as indicated by the arrows a, a; that is,

as viewed in Fig. 1, the roll at the left rotates clockwise and the rollat the right counterclockwise. At each end of the rolls I there ispreferably provided a dam 2 so as to form with the rolls a reservoir forthe material being fed between them. A tank 3 containing the supply ofmaterial to be dried is arranged in any convenient position for feedingthe material into the space between therolls. As shown, the tank ismounted at an elevation above the rolls I so that the suspension may befed by gravity through the pipe 4. A valve 5 may. be provided toregulate the flow. The accumulated feed stock in the reservoir betweenthe dams 2 is indicated at 6 in Fig. 1. This feed stock flows onto therolls I, forming a thin layer 1 on each of the rolls. The rolls areheated in any convenient manner to a temperature which should besomewhat v above the boiling point of water. For this purapparatus fordrying materials of the class deshown in the lower part of Fig. 1. v

The apparatus consists essentially of a pair of drying rolls or drums I,l arranged for rotation in opposite directions around substantiallyhoripose any heating means known to the art may be employed. The thincohesive film of moist solids thus formed is peeled from the dryingrolls at points which conveniently may be located about from the rollpass 8. For this purpose a pair of knives 9 are arranged adjacent and atan angle to the surfaces of the rolls. As the films leave the rolls theypass downwardly over inclined tables or guides l0 into spiral conveyorsII which break up the dried material and carry it to a succeedingstation for further processing, packaging, or storing, as may bedesired.

An essential feature of our invention resides in the provision of meansfor reclaiming excess material which otherwise would be wasted. Theamount of Waste in drying certain types of material is veryconsiderable. This is true, for example, with cereal products, animalfeed, .products containing whey and casein, and similar products, duringthe manufacture of which heavy suspensions of solid matter in liquidsare extending lengthwise of the rolls. The bottom l3 of the trough I2 ispreferably inclined, as shown in Fig. 2. At its lower end it is providedwith a discharge outlet; l4 leading to a pump i5. A pipe I6 leading froma source of supply of the same feed stock that is being fed to the rollsis arranged so as to discharge a quantity of the feed stock into theupper end of the trough l2. This serves to washout the surplus materialaccumulating in the trough so that it passes freely out through theconduit H to the pump. A pump thoroughly mixes the solution and forcesit through the pipe I! to be returned to the supply tank 3 where it ismixed with the main body of the feed stock.

The feed stock introduced through the pipe i6 may be provided by aseparate tank or other source of supply but we prefer that it be drawnfrom the main tank 3, thus insuring that the mixture in the trough l2will be of the same composition as that which is being fed to the rolls.J Thus the pipe l6 may be connected to the tank 3 or to the pipe 4 bythe pipe l8. A valve l9 provides convenient means for regulating theamount of feed stock which is by-passed into the trough l2. It will beunderstood that only a sufiicient amount to wash out the materialaccumulated in the trough l2 need be bypassed through the pipe IS.

A leveling bar is arranged in proximity to the under surface of each ofthe rolls l, the lower edges of these bars preferably being flangeddown:

wardly as at 2|. The purpose of the leveling bars is to smooth out thefilm of material on the rolls and to dislodge and remove fibrous orother undesirable lumps or particles occurring therein.

A novel feature of our invention resides in arranging the leveling barsabove the trough 12 in such a way that the surplus material removedthereby is delivered to the trough. This material is then washed out ofthe trough together with the material dripping from the rolls, beingthoroughly mixed with the separate quantity of feed stock introducedinto the upper end of the trough so as to prepareit for reintroductionto the supply tank to be re-applied to the heated surfaces of the rolls.It will be observed that with my arrangement this will be accomplishedwithout altering the composition and without diluting the suspension.

We have found that the drying operation may be performed-very rapidlywith the arrangement described inasmuch as the increased amount of feedstock dripping from the rolls at higher speeds of operation does notrepresent an increased waste, The increased speed of operation isfurther assisted by the provision of means for further drying the moistfilm as it leaves the ,rolls. This may be accomplished by directing astream of warm air or other drying fluid against the film. For thispurpose we provide perforated pipes 22 arranged to direct air againstboth surfaces of the films I. The perforated pipes 22 are connected toany suitable source of supply (not shown) by the conduits 23. Asignificant feature of our preferred arrangement resides in directingthe air against both sides of the film. We have found that it is quiteimportant to direct air against the under side of the film because thereis formed, between the film passing down over the guides l0 and therolls, a pocket 24 in which moist air accumulates. However, we havefound that this accumulated moisture is rapidly driven out by means ofthe air forced through the inner drying pipes 22.

It will be understood that various modifications can be made in theparticular arrangement described. For example, the feed stock could beapplied to the rolls other than as specifically i1- lustrated. It mightbe sprayed onto the rolls or run onto the rolls through a suitableconveyor. It will be understood also that our apparatus is advantageousin the manufacture of a wide variety of materials. The invention isparticularly advantageous, however, as applied to the drying of heavysuspensions of solids in liquids such as whey or milk. In this categorymay be named suspensions of any suitable ground material such as seedmeal high in protein, e. g. soy bean meal, in whey or skim milk. Anexample of such a suspension is a mixture of whey, which alone contains6 per cent. solids, with enough soy bean flour to give a total solidscontent of 50 per cent. The term suspensions as used herein and in theappended claims is intended as a term of description and not oflimitation, and is to be understood as including any materials which areequivalent to those named by way of example. The same is true of otherterms and expressions used herein, and we have no intention in the useof such terms and expressions of excluding any equivalents of theinvention described, or of portions thereof.

We claim:

1. Apparatus for drying suspensions of solids in liquids comprisingadjacent drying rolls arranged for rotation in opposite directionsaround substantially horizontal parallel axes with the adjacent surfacesthereof moving downwardly, means for heating the surfaces of said rolls,means for feeding suspensions into the rolls, a trough positioned belowthe adjacent surfaces of the rolls for collecting material drippingtherefrom, leveling means positioned above said trough and extendingsubstantially the full length of the drying surfaces for removing excessmaterial from the surfaces of the suspensions on the rolls, and meansfor feeding a separate quantity of the suspensions into said trough formixing with said collected material and excess material to produce amaterial suitable for mixing with the suspensions entering the rolls.

2. Apparatus for drying suspensions of solids in liquids comprisingadjacent drying rolls arranged for rotation in opposite directionsaround substantially horizontal parallel axes with the adjacent surfacesthereof moving downwardly, means for heating the surfaces of said rolls,means for feeding suspensions into the rolls, an inclined troughpositioned below the adjacent surfaces of the rolls for collectingmaterial dripping therefrom, means positioned above the trough forremoving excess material from the surfaces of the suspensions on therolls, means for feeding a separate quantity of the suspensions into theupend of said trough to wash said collected materials from the trough,and means for mixing said materials with the suspensions entering therolls.

3. Apparatus for drying suspensions of solids in liquids comprisingadjacent drying rolls arranged for rotation in opposite directionsaround substantially horizontal parallel axes with the adjacent surfacesthereof moving downwardly, means for heating the surfaces of said rolls,a tank and means associated therewith for discharging suspensions intothe rolls, a trough positioned below the adjacent surfaces of the rolls,means connected to said tank for conveying a portion of the suspensionsinto said trough independently of said discharging means, and means forreturning suspensions from said trough to said tank.

suspensions into the rolls, a trough positioned below the adjacentsurfaces of the rolls, levelers.

arranged above said trough for cooperation with said rolls, meansconnected to said tank for conveying a portion or the suspensions intosaid trough, and means for returning suspensions from said trough tosaid tank.

5. Apparatus for drying suspensions of solids in liquids which comprisesan element'having a drying surface. a reservoir for feed stockconsisting of such a suspension, said reservoir being 10- cated at apoint removed from the drying surface, a second reservoirarranged tohold feed stock in contact with the drying surface, means for conveyingthe feed stock from the first reservoir to the second reservoir forapplication to said surface to form a cohesive film, means forcollecting the excess material resulting from the formation of saidfilm, means for by-passing a portion of the feed stock from the firstreservoir around the second reservoir to said collecting means formixing with said excess material, and means for conveying the resultingmixture to the first reservoir.

ARTHUR C. BEARDSLEE. GEORGE W. W'IL SON.

